 It frankly is not the moderator's job to challenge that. It should be up to each candidate to rebut one another and probe the other's policy or character weaknesses. If Trump or Biden fail to do so, over the 90 minutes, the moderator should avoid filling in the gaps. In other words, let you decide. Biden can criticize Trump's answers. Trump can criticize Biden's answers. Let him answer. Let him go at it a little bit.